Means for controlling the blast valve and contacts of a gas blast circuit breaker



Aug. 15, 157 j w. BEATTY ET AL 3,336,453

MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLASTCIRCUIT BREAKER Filed Dec. 29. 1964 5 $heetsSheet l F/GJ.

ATMUJPHEfi/O PRESSURE 70Gb PRESSURE uvvavrom: JOHN W. 55%17'7'), R/cH/uwH. M/LLER A TTOR/VEY Aug. 15. 197 J.W. BEATTY ET AL MEANS FORCONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKERFlled Dec. 29. 1964 5 Sheets-Sheet 2 H/G/v PRESSURE INVENTORS. 7 JOHN W.BEATTY R/cHA/w H. M/LLER ATTORNEY Aug. 15, 1967 J E Y ET AL 3,336,453

MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLASTCIRCUIT BREAKER 5 Sheets-Sheet 5 Filed Dec. 29. 1964 IN VENTORS.

ATTORNEY mg. 15, W67 J.W. BEATTY ET AL 3 9 MEANS FOR CONTROLLING THEBLAST VALVE AND CONTACTS OF A GAS BLAST CIRCUIT BREAKER Filed Dec. 29,1964 5 Sheets-Sheet 4 ATTORNEY Aug. 15, H967 ,w BEATTY ET AL 3,336,453

MEANS FOR CONTROLLING THE BLAST VALVE AND CONTACTS OF A GAS BLASTCIRCUIT BREAKER Filed Dec. 29, 1964 5 Sheets-Sheet 5 /7Za m4 /72 L70 m1-/7 O O O INVENTORS.

JOHN W. 55/477), R/CHARD M/LLER 5y 0mm 7L A ATTORNEY United StatesPatent 3,336,453 MEANS FOR CONTROLLING BLAST VALVE AND CUNTACTS OF A GASBLAST CHRQUH" BREAKER John W. Beatty, Newtown Square, and Richard H.Miller, Berwyn, Pa., assignors to General Electric Company, acorporation of New York Filed Dec. 29, 1964, Ser. No. 421,776 17 Claims.(til. 200-148) This invention relates to an electric circuit breaker ofthe gas blast type and, more particularly, relates to means forcontrolling the blast valve and movable contacts of such a circuitbreaker.

In the circuit breaker of the present invention, there is a pair ofrelatively movable contacts that can be separated to draw an arctherebetween and a blast valve that is operable at the time ofcontact-separation to cause a blast of pressurized gas to flow throughthe arcing region to aid in extinguishing the arc. The blast valvecomprises a movable valve member that can be operated from anormally-closed position to an open position to create the gas blast.After a period of time suflicient to insure extinction of the arc, themovable blast valve member is returned to its normally-closed positionto terminate the blast, thereby preventing such wastage of pressurizedgas as would result from continuation of the blast. The con tacts areheld in open position after the blast valve closes, thus maintaining thecircuit open.

An object of our invention is to provide a new and improved mechanismfor controlling the blast valve and contacts in this manner.

In certain prior mechanisms for controlling the blast valve andcontacts, the same pressurized fluid has been used for both returningthe movable blast valve member to its closed position and for holdingthe contacts in open position. When it has been desired to close such acircuit breaker, the pressure of the pressurized fluid holding thecontacts open had to be reduced to a predetermined level, as by venting,before closing motion of the contacts could begin. Thereafter, the speedof closing depended upon the rate of venting. In certain circuit breakerapplications, it is disadvantageous to rely upon such venting because itrequires a rather long time that unduly delays initiation ofcontact-closing motion. Another disadvantage of relying upon suchventing is that closing times tend to vary rather widely with variationsin the initial fluid pressure holding the contacts open.

Another object of our invention is to provide an operating mechanismcapable of controlling the motion of the blast valve and contacts in thegeneral manner set forth above but capable of responding faster to aclosing signal and capable of more precisely controlling contact-closingmotion than a mechanism that relies upon the above-described venting ofpressurized fluid for initiating and controlling closing motion.

Another object is to provide a blast valve and contact operatingmechanism which can initiate circuit breaker opening in response to arelatively low-force input signal and within a very short time afterreception of the input signal.

Still another object is to provide a high speed blast valve and contactoperating mechanism that is highly compact and can be located in a smallgas-filled tank surrounding the contacts.

Another object is to provide an operating mechanism which has openingtime characteristics that are relatively insensitive to minor changes inthe position of an operation-initiating part.

In carrying out our invention in one form, we provide a gas blastcircuit breaker that comprises a contact movable from a closed positionto an open position to develop 3,335,453 Patented Aug. 15, 1967 an arc,a blast valve member movable from a closed position to an open positionto create an arc-extinguishing blast, and a tank that is adapted tocontain a supply of high pressure gas in which the contact is located.Coupled to the movable blast valve member is an actuating piston thathas an opening surface on which pressurized fluid is adapted to act in ablast valve-opening direction and a closing surface on which pressurizedfluid is adapted to act in a blast valve-closing direction. Means isprovided for supplying high pressure fluid to the opening surface of theactuating piston to drive the piston through an opening-stroke thatopens the blast valve member. Actuating means coupled to the contact isprovided for transmitting contact-opening motion from the actuatingpiston to the contact when the actuating piston moves through itsopening stroke. Means is also provided for supplying high pressure fluidto the closing surface of the piston after the opening stroke to thencause closing of the blast valve member. When the blast valve member isclosed, the closing surface is vented to a low pressure region, and thisremoves from the closing surface high pressure fluid that previouslyacted on the contact in an opening direction. Closing means is providedfor causing the high pressure gas in the tank when the closing surfaceof the blast valve piston is vented to the low pressure region to exerta net force on the contact acting in a direction to drive the contacttoward closed position. Latching means is provided for holding thecontact in an open position against this closing means when the closingsurface of the piston is vented to the low pressure region, and closingcontrol means is provided for releasing the latching means to permit theclosing means to drive the contact into closed position.

For a better understanding of our invention, reference may be had to thefollowing description taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a schematic side elevational view partly in section of acircuit breaker embodying one form of our invention.

FIG. 2 is a cross sectional view taken along the line 2--2 of FIG. 1.

FIG. 3 is a schematic cross sectional view taken along the line 3-3 ofFIG. 2; FIG. 3 shows the circuit breaker in its normally-closedposition.

FIG. 4 is a schematic cross sectional view similar to FIG. 3 exceptshowing the circuit breaker in a position in which its blast valve andcontacts are fully open.

FIG. 5 is a schematic view partly in section also showing the circuitbreaker in its normally-closed position.

FIG. 6 is a view similar to FIG. 5 except showing the circuit breaker inits fully-open position. FIG. 6 illustrates the position of the partswhen the circuit breaker has just entered its fully-open position, and,accordingly, the normally-closed blast valve is still open but is inreadiness to reclo-se.

General description of circuit breaker Referring now to FIG. 1, thecircuit breaker shown therein comprises a metallic tank 10 filled with ahighly pressurized gas, preferably air. This tank 10 is mounted on atubular insulating column 12, preferably of porcelain, that isolates thetank from ground.

Projecting into the tank ill from opposite sides thereof are twoinsulating bushings 14 and 16. Each of these bushings comprises acentrally-disposed rigid conductor 18 and a tubular insulator 20surrounding and supporting the conductor 18 and insulating it from thetank 10 when the circuit breaker is open.

At the inner end of each of these conductors 18 is a stationary contact22;. Cooperating with their respective stationary contacts 22 are a pairof movable contacts 24, each of which is pivotally mounted at 26 on acentral a casting 28 that is mounted on the tank It) and electricallyconnected thereto. When the circuit breaker is in its closed position,as shown in FIG. 1, an electrical circuit extends through the circuitbreaker via one conductor 18, one pair of contacts 22, 24 through thecentral casting 28, the other pair of contacts 22, 24, and the otherconductor 18.

During a circuit breaker opening operation, the contacts 24 aresimultaneously operated from their closed position of FIG. 1, into theiropen position by driving a centrally disposed crosshead 30 in a downwarddirection. This crosshead 30 is coupled to the contacts 24 by means oflinks 32, each of which is pivotally, connected at its opposite ends toa contact 24 and the crosshead 3tB. Whcn the crosshead moves downwardlyfrom its position of FIG. 1, it acts through links 32 to pivot themovable contacts 24 about their pivots 26, moving the upper portion ofeach movable contact 24 toward the central casting, thus separating themovable contacts 24 from their respective stationary contacts 22.

The above-described contact-separation produces an arc between thecontacts of each pair, and this arc is extinguished after a shortinterval by a blast of pressurized gas which flows through the arcingregion. This gas blast is produced by opening a normally-closed blastvalve 35 just prior to the time the contacts separate to form the arc.The normally-closed blast valve 35 comprises a movable valve member 36that is located in a blast passage 37. This blast passage 37 extendsupwardly to atmosphere from two nozzles 38 respectively located adjacentthe two arcing regions. When the movable blast valve member 36 is movedin a downward opening direction from its position of FIG. 1, pressurizedgas flows from the tank 1!) through the nozzles 38 and blast passage 37via paths such as illustrated by arrows 40. After the movable blastvalve member has remained in open position for a sufficient period toeffect arc-extinction, it is returned to its closed position of FIG. 1to terminate the gas blast. This valve-closing prevents the pressurizedgas in the tank from being wasted by continued flow fro-m the tank aftera circuit-interrupting operation. The contacts are normally caused toremain open after an interrupting operation to maintain twoseries-related intercontact gaps in the circuit through the circuitbreaker.

Operating mechanism for blast valve and contacts For controlling themovable blast member 36 and the movable contacts 24 in theabove-described manner, a pneumatically-controlled operating mechanism56 located in the hollow casting 28 is provided. This operatingmechanism 50 is best shown in FIG. 3. It comprises a stationarycentrally-located cylinder 52 that is normally filled with pressurizedgas from the tank 10. This pressurized gas is supplied from the tankthrough a feed passage 56 having ports 57, 58, 59 and opening into theinterior of the stationary cylinder 52. The stationary cylinder 52 has alower end wall 53 and an upper end wall 54.

Slidably mounted within the stationary cylinder 52 is a contact-openingdashpot piston 69 that is rigidly connected to the crosshead 30. Thedashpot piston 66 has a vertically-extending piston rod 61 that extendsthrough the lower end wall 53 of cylinder 52 and is suitably joined to aportion 150 of the crosshead 30. In this latter respect, a threadedportion of the piston rod 61 extends through the portion 150 ofcrosshead 3i), and a nut 62 is threaded thereon to clamp the crossheadportion 156 between the nut 62 and a shoulder on the piston rod 61. Alsosecured to the crosshead 30 is a plurality of rods 64 that projectupwardly from the crosshead about the outside of cylinder 52. As willsoon appear more clearly, contact-opening forces are transmitted throughthese rods 64 to effect downward opening motion of crosshead 35.

The rods 64 bear at their upper end against a blast valveandcontact-actuating piston 65 that is integral with the movable blastvalve member 36. This piston 65 is of an annular form and surrounds thecylinder 52 with a sliding fit. A suitable O-ring seal 63 is preferablyprovided to prevent pressurized air from leaking past the piston 65along the outer surface of cylinder 52. The movable blast valve member36 is of a cylindrical form and closely surrounds the upper end wall 54,which has a circular outer periphery slidably fitting within thecylindrical blast valve member 36. The outer periphery of the movableblast valve member 65 is slidably mounted within a cylindrical portion67 of the stationary casting 38 that cooperates with a suitable pistonring on piston 65 to prevent pressurized air from leaking along thisouter periphery into the space It)? beneath the piston 65.

The movable blast valve member 36 can be driven in a downward openingdirection by supplying pressurized air to an actuating chamber 66located immediately above the blast valveand contact-actuating piston65. In this connection, the upper end wall 54 of cylinder 52 extendsradially outward past the outer periphery of the cylinder 52 and definesan upper wall for this actuating chamber 66. An inlet passage 69communicates with this actuating chamber 66. When high pressure air ispermitted to flow through this inlet passage 69, as will soon bedescribed, it will flow into the actuating chamber 66 and build up apressure that acts on the upper surface 65a of the blast valveandcontact-actuating piston '65 to drive the piston 65 in a downwardblast-valve-opening direction. This upper surface 65a of the piston 65is referred to hereinafter as the blast valve-opening surface.

This downward movement of the blast valve-and contact-actuating piston65 withdraws the upper sealing surface 36a of the movable blast valvemember 36 from its seat, thereby producing the previously-describedblast of gas along the paths 40 of FIG. 1. FIG. 4 illustrates the blastvalve member 36 in its fully open position with the high pressure airstreaming past its upper surface. Downward movement of the blastvalve-and contact-actuating piston 65 into its position of FIG. 4 isalso transmitted through the rods 64 and the crosshead 30 to the movablecontacts 24. This causes these contacts to open and draw a pair of arcsadjacent the nozzles 38. These arcs are extinguished after a shortperiod by the gas blast through the nozzles.

Pilot valve and its operation For controlling the flow of high pressureair into the blast valve actuating chamber 66 so as to control movementof the blast valve member 36, a normally-closed pilot valve 70comprising a movable pilot valve member 71 is provided. Referring toFIG. 3, there is a flow passage 72 located centrally of the end wall 54and a connecting passage 73 that connects the central passage 72 withinlet passage 69. When the movable pilot valve member '71 is in itsuppermost position of FIG. 3, an annular sealing surface thereon abutsagainst a suitable seat on the end wall 54 and thus prevents highpressure air from entering the passages 72, 73 and 69. But when themovable pilot valve member 71 is driven in a downward opening directioninto its position of FIG. 4, high pressure air is permitted to flow pastthte pilot valve via passages 56, 57, 72, 73, 69 into the blast-valveactuating chamber 66, thus driving the blast valve-and contact-actuatingpiston 65 in a downward direction to effect the above-described openingof the blast valve member 36 and the movable contacts 24.

Poitassisting in opening the pilot valve member 71 and for holding thepilot valve member 71 in its open position for the desired period, thepilot valve member 71 is provided with a booster piston 75. This boosterpiston 75 is secured to the upper end of an upwardlyextending extensionof pilot valve member 71. The booster piston 75 is slidably mountedwithin a booster cylinder 76, and a compression spring 77 is locatedbetween the booster piston 75 and the end wall 54 to exert an upwardbiasing force on the movable pilot valve member 71 that normally holdsthe movable pilot valve member in its closed position of FIG. 3. Anactuating chamber 78 for the booster piston 75 is located between theupper surface 79 of the booster piston and the upper end wall of thebooster cylinder 76.

The actuating chamber 78 for the booster piston is normally vented toatmosphere through a passage 80 that extends through the extension ofthe movable pilot valve member 71 into the central flow passage 72. Thecentral flow passage 72 is, in turn, normally vented to atmospherethrough a passage 82 and a slot 84 formed in the inner cylindricalsurface of blast valve member 36 and aligned with passage 82 when theblast valve is closed. When the movable pilot valve member 71 is movedin a downward direction out of its normally-closed position of FIG. 3,an enlarged portion 85 of its extension covers the entry port 86 to thepassage 82, thereby blocking communication between passages 72 and 82,thus sealing the central flow passage 72 from atmosphere. Thus, when themovable pilot valve member 71 is moved in a downward opening direction,the central flow passage 72 is no longer vented to atmosphere and highpressure air flows into the central passage 72 and through the passage80 into the actuating chamber 78 for the booster piston. This results ina rapid pressure buildup above the booster piston 75 that provides asupplemental opening force for driving the booster piston 75 and themovable pilot valve member 71 downwardly toward their fully-openposition of FIG. 4. As will be explained in greater detail hereinafter,this rapidly-developed supplemental force helps to rendercontact-opening times substantially independent of minor variations inthe instant at which the pilot valve member starts its opening movement.

Reset of the movable pilot valve member 71 to its closed position ofFIG. 3 is accomplished at a subsequent point by supplying high pressureair to the space 87 beneath the booster piston 75. For supplying thishigh pressure air for resetting purposes, a pilot valve reset passage 90is provided leading into the reset space 87. This pilot valve resetpassage 90 has an inlet that is located in vertical alignment with thepassage 73, but no effective communication normally is present betweenpassages 73 and 90. However, when the movable blast valve member 36moves into its fully-open position of FIG. 4, an interlock slot 92formed in its inner surface establishes effec tive communication betweenpassages 73 and 90. This permits high pressure air to flow throughpassages 73 and 90 via interlock slot 92 and into the reset space 87,thereby building up a pressure in the reset space 87. This pressure actsin an upward direction on the lower surface 75b of booster piston 75.(Note that lower surface 75b includes upper and lower area portions asdesignated in FIG. 3.) Since force on the lower surface 75b of thebooster piston 75 acts in a direction to close the pilot valve 71, thensurface 75b will be referred to hereinafter as the pilot valve-closingsurface. Since piston 75 has a substantially larger lower surface 7512than upper surface 79, there is a net force on the piston 75 acting in adirection to return the movable pilot valve member 71 from its positionof FIG. 4 to its normallyclosed position of FIG. 3. The compressionspring 77 also helps to provide force for this resetting operation. Thespace immediately surrounding the cup-shaped booster piston 75 is ventedto atmosphere through a passage 93 to prevent air from leaking betweenopposite sides of the booster piston along the outer surface of thepiston.

Pneumatic coupling for pilot valve control 'The other piston 102, whichwill be referred to as the control piston, is connected to an operatingrod 104 which extends through an opening in the lower wall 53 of thecylinder 52 and then, as shown in FIG. 1, through a sealed opening inthe wall of tank 10 and then through the interior of the insulatingsupport column 12. Suitable operating means, shown in FIGS. 5 and 6, isprovided at the lower end of the rod 104 for operating the rod 104 in adownward direction. As will soon appear more clearly, downward movementof the rod produces opening of the circuit breaker, and upward movementof the rod from its open position produces closing of the circuitbreaker. The rod 104 preferably passes through the lower end wall 53 ofcylinder 52 via a central bore 107 in the dashpot piston rod 61.

When the circuit breaker is in its closed position of FIG. 3, highpressure air is present adjacent both the upper and lower surfaces ofboth of the two pistons and 102. This follows from the fact that highpressure feed line 56 communicates via ports 57 and 58 with the interiorof cylinder 52.

When the operating rod 104 is driven downwardly to pull the piston 102in a downward direction, the volume between the two pistons quicklyincreases, producing a sudden drop in pressure in this volume. This dropin pressure permits the high pressure air immediately above piston 100to develop a large downward force that drives the pilot piston 100downwardly in follow-up relationship to the lower piston 102. Thisdownward motion of pilot piston 100 opens the pilot valve and thusbegins movement of the blast valve member 36 and the contacts 24 towardtheir respective open positions, as described hereinabove.

The upper piStOn 100 continues moving in pneumatically coupled follow-uprelationship to the lower piston 102 until the lower piston crosses theport 58. When this occurs, high pressure air flows through the port 58into the space 105 between the two pistons, equalizing the pressure onopposite sides of the upper piston 100 to, in effect, break thepneumatic coupling between the two pistons 100 and 102.

But despite this uncoupling of the two pistons 100 and 102, the upperpiston does not immediately return to its normal position of FIG. 3.This is the case because the booster chamber 78 has then filled withhigh pressure air acting in a downward direction on the booster piston75 and the movable pilot valve member 71. The downward force exerted bythis high pressure air holds the pilot valve member 71 in its fully openposition until the movable blast valve member as has reachedsubstantially its fully open position.

Closing of the pilot valve near the end 0] a circuit breaker openingoperation When the movable blast valve member 36 does reachsubstantially its fully open position of FIG. 4, its interlock slot 92establishes communication between passages 73 and 90, as previouslydescribed. High pressure air then flows through '73 and 00 via slot 92and soon builds up a high pressure in the pilot valve reset space 87.The rate at which this pressure buildup occurs is controlled by amanually-adjustable throttle valve 100 located in the passage 90. Whenthe pressure in the pilot valve reset chamber 87 has built up to apredetermined level, a sufficient upward force is exerted on the boosterpiston 75 to return the movable pilot valve member 71 to itsnormally-closed position of FIG. 3.

Closing of the blast valve in response to pilot valve closing Themovable blast valve member 36 remains in its fully-open position of FIG.4 until the movable pilot valve member 71 has returned to substantiallyits normally-closed position of FIG. 3. The force for blast valveclosingis developed in a blast-valve closing chamber 109 at the lower side ofthe blast-valve piston 65. This cham ber 109 is normally vented toatmosphere. But when the pilot valve member 71 returns to its closedposition while the blast valve member 36 is in its fully-open positionof FIG. 4, chamber 109 is no longer vented to atmosphere and apressure-equalizing passageway is present connecting blast-valveactuating chamber 66 and the blast-valve closing chamber 169 at thelower side of the blast valve piston 65. This pressure-equalizingpassageway is constituted by passages 69, 73, 72, 86, 82 and 110 and isopen when the movable pilot valve member 71, 85 uncovered port 86 nearthe end of its abovedescribed closing motion. Passage 116 normally ventsthe blast valve closing space 109 to atmosphere through passages 82 and84, as seen in FIG. 3. But when the blast valve member 36 is in itsfully open position, passage 82 is shut oflf from atmosphere by reasonof slot 84 in the movable blast valve member moving out of alignmenttherewith. When high pressure air flows from the blastvalve actuatingchamber 66 to the closing chamber 189 at the lower side of the blastvalve piston 65 through the above-described equalizing passage, thepressures on opposite sides of the blast valve piston 65 equalize. Itwill be apparent from FIGS. 3 and 4 that the blast valve piston has alarger area exposed to pressure in chamber 109 than to pressure inchamber 66. Accordingly, there is then a net force acting in an upwarddirection on the blast valve piston 65, and this force acts to returnthe movable blast valve member 36 to its closed position.

The above-described interlocking relationship between the operation ofthe pilot valve member 71 and the blast valve member 36 is described angreater detail and is claimed in our application S.N. 421,777, filedDec. 29, 1964, and assigned to the assignee of the present invention.

In order to prevent any substantial build-up of pressure in the blastvalve closing chamber 169 while the pilot valve member 71 is in its openposition, a vent passage in the form of an external groove 115 isprovided in the movable pilot valve member 71. This vent passage 115vents the passages 110 and 82 to atmosphere through a vent 116 in theend cap 54 aligned with the vent passage 115 while the movable pilotvalve member 71 is in its open position of FIG. 4. This venting means115, 116 insures that any leakage of high pressure air into blast valveclosing chamber 189 (when the blast valve is open and vent 84 in theblast valve member 36 is therefore unavailable) will not build up asignificant pressure in chamber 109. Preventing such pressure buildupassures that closing of the movable blast valve member 36 will not beinitiated until the pilot valve member 71 has returned to nearly itsfully closed position of FIG. 3.

The rate at which pressure is built up in blast valve closing space 109can be controlled by a needle valve 120 that can be adjusted to controlthe rate of flow through the pressure equalizing passage 69, 73, 72, 86,82, 110.

When the blast valve member 36 is in its closed position, illustrated inFIG. 3, it has a' larger area exposed to pressure acting in a closingdirection than in an opening direction, and this results in a forcenormally holding the blast valve member 36 closed. To assure that theblast valve member 36 remains closed even through there might be a largedrop in tank pressure, a plurality of light compression springs 119,shown in FIG. 2, are provided in the chamber 109 beneath the blast valvepiston. These springs 119 act in an upward direction against the blastvalve piston 65 to resist downward opening movement of the blast valvemember 36.

When the movable blast valve member 36 closes, as hereinabove described,in response to prior pilot valve closing, all the chambers upstream fromthe sealing surface of the pilot valve member 71 are vented toatmosphere. The manner in which such venting takes place can best beseen in FIG. 3, where both the pilot valve member 71 and blast member 36are shown in their respective closed positions. Referring to FIG. 3, itwill be apparent that the blast valve closing chamber 109 is vented toatmosphere through passages 110, 82, and 84; whereas the blast valveactuating chamber 66 is vented-to atmosphere through passages 69, 73,72, 82 and 84. The booster piston actuating chamber 78 is vented toatmosphere through passages 86, 82 and 84. The pilot valve reset chamber87 is vented through small bleed passages 123 and 124 communicating withpassage and then through passages 82 and 84. Venting of these chambersat this time serves the desirable function of assuring that on asubsequent operation, pressures will be built up in these chambers fromthe same reference level, i.e. atmospheric pressure. This helps toassure that the blast valve-opening and contact-opening times will notvary appreciably from one opening operation to the next. Also ventingthe blast valve closing chamber 109 assures that there will be nopressure in this chamber acting downwardly on the ends of rods 64 tointerfere with a subsequent circuit breakerclosing operation, when therods 64 more upwardly through chamber 109, as will soon be described.

The passages 123 and 124 leading into pilot valve reset chamber 87function as a portion of a pneumatic lock for folding the pilot valveclosed during the period between return of the pilot valve to its closedposition and return of the blast valve member 36 to its closed position.More specifically, these passages 123, 124 assure that the pilot valvewill not be opened unintentionally by any pressure differentialdeveloping on opposite sides of the booster piston 75 while the blastvalve member 36is open and booster chamber 78 is therefore unvented. Inthis regard, these passages 123, 124 maintain communication betweenchamberas 78 and 87 on opposite sides of the booster piston 75 while thepilot valve is in closed position. Thus, any high pressure present inbooster piston actuating chamber 78 will also be present in the resetchamber 87, and there will be a net force on booster piston 75 acting ina pilot valve-closing direction to hold the pilot valve closed in viewof the relatively large cosing area 75b as compared to opening area 79.

On an opening operation, the high pressure air that flows throughpassage 80 will fiow almost entirely into the booster piston actuatingchamber 78, with little entering the reset chamber 87 through passages123, 124. This is the case because passage 123 is a small bleed passageand, due to its small size, does not permit much high pressure to flowinto chamber 87 during the brief period before the passage 123 iscovered by an enlarged portion 126 on movable pilot valve member 71.Near the end of a pilot valve-opening stroke, this enlarged portion 126acts as a dash-pot piston in a cylinder 127. Air displaced from cylinder127 by piston 126 is forced through passage 124 which becomesprogressively more restricted as the pilot valve member 71 reaches theend of its opening stroke.

Holding the contacts and the control piston in open position After thecrosshead 30 has been driven downwardly by the blast valve-andcontact-actuating piston 65 to open the contacts 24, as describedhereinabove, the crosshead 30 is latched in its open position by amechanical latch 13%) shown in FIG. 5. This latch 13th holds thecrosshead 30 and the interconnected contact 24 in their open positionsof FIGS. 4 and 6 despite the above-described return of the blast valvemember 36 to its closed position. In this connection, a suitable roller132 carried by the crosshead 30 normally holds the latch 132' in itsreleased position shown in FIG. 5, where the circuit breaker is depictedclosed. When the circuit breaker is operated toward open position andthe roller 132 moves downwardly past the lower end of latch 131), areset spring 134 drives the latch clockwise about its stationary pivot135 against a stop 136. The latch is then in its latching postion ofFIGS. 4 and 6, where it can prevent upward movement of the crosshead 30through interference with roller 132, thus holding the contacts open. 7v

The control piston 162 that was moved downwardly to initiate pilot valveopening is similarly held in its loWermost position of FIG. 6 by a latchschematically depicted at 140. A closure-initiating spring 142 acts onoperating rod 104 to bias the piston 102 upwardly toward its initialposition of FIG. 5, but the latch 140 retains the piston 102 in itslowermost position so long as it is desired to hold the circuit breakeropen.

The latch 140 acts on a force-transmitting linkage 170 which is coupledto the rod 104. This force-transmitting linkage 170 comprises aplurality of cranks 172, 173, and 174, which are respectively pivotallymounted on stationary pivats 172a, 173a and 174a. interconnecting thecranks 172 and 173 is a link 1'75 pivotally connected at its oppositeends to the two cranks. Interconnecting the cranks 174 and 173 is a link176 pivotally connected at its opposite ends to these two cranks. Thecrank 174 carries a latching roller 177 which the latch 140 cooperateswith to hold the linkage in its position of FIG. 6.

Closing operation of the Circuit breaker Closing of the circuit breakeris initiated by suitably tripping the latch 140 of FIG. 6. This is donewith a solenoid 144 that, upon energization, drives its armatureupwardly to engage the latch 140 and pivot it counterclockwise about itsstationary pivot 146 against the bias of a latch-reset spring 145. Thisremoves the restraining eifect of the latch 140 from the latching roller17?, permitting the closurednitiating spring 142 near the top of rod 104to drive the control piston 102 and operating rod 104 upwardly. Upwardmovement of the operating rod 104 moves the linkage 1'70 into itsunlatched position of FIG. 5.

The above-described upward movement of the operating rod 104 is used forreleasing the contact-restraining latch 130 after a predetermined amountof such upward movement of the operating rod 104. Release of thecontact-restraining latch 130 is ettected by means of a latchreleasinglinkage 180 that is coupled between the operating rod 104 and thecontact-restraining latch 130. This latch-releasing linkage 180comprises an input arm 181 that is pivotally mounted on a stationarypivot 182 and an output arm 183 that is pivotally mounted on astationary pivot 104. These arms 181 and 183 are interconnected by alink 185 that is pivotally connected at its opposite ends to therespective arms. The input arm 181 has a pivotal connection 186 at itsouter end with the operating rod 104. The output arm 103 carries aroller 107 that is adapted to engage the contact-restraining latch 130.When the operating rod 104 moves upwardly, it acts through parts 181 and185 to pivot arm 103 clockwise about its pivot 184, causing roller 187to engage the latch 130 and pivot it in a counterclockwise releasingdirection. After a predetermined upward movement of operating rod 104,the latch 1350 is released.

Release of the latch 130 allows the high pressure air acting on thecrosshead 30 to drive the crosshead upwardly, thereby pivoting themovable contact 24 of FIG. 4 in a counterclockwise direction aboutstationary pivot 26 to effect circuit breaker closing. There is anupwardlyacting pneumatic bias on the crosshead 30 because the rods 64extended into the vented chamber 109 and therefore had no high pressureair acting downwardly on them. There is thus a larger area of thecrosshead structure 30, 64 exposed to pressure acting in an upwardclosing direction than to pressure acting in a downward direction.

The contact-closing speed is controlled by piston 150 attached to thecrosshead 30. This piston 150 is slidably mounted in a stationarycylinder 152 having a large opening 154 therein. Initial closing motiontakes place at high speed since the air in cylinder 152 ahead of theupwardly moving piston 150 can be freely expelled through opening 154.But when the upwardly moving piston 150 passes the opening 154, the airahead of it is forced through a restricted passage 156 at a controlledrate, thus providing a dashpot action that smoothly terminates upwardclosing movement of the piston 150 and the connected contacts.

10 To prevent a retarding low pressure from being developed above pistonduring downward opening movement, a passage 157 containing a check valve158 is provided in the piston to allow air to flow upwardly into thespace above the piston should a reduced pressure be developed in thisspace.

To prevent a retarding low pressure from being developed behind theopening dashpot piston 60 during closing, a passageway is providedleading from the high pressure tank into the cylinder space behind thepiston 60. A check valve 162 in this passage 160 allows air to flowupwardly therethorugh into the space behind the piston 60 as it movesupwardly. This check valve prevents air from flowing through passage 160during an opening operation.

When the control piston 102 moves upwardly during the abovedescribedclosing action, the high pressure air in cylinder 52 ahead of the piston102 is expelled first primarily through the port 58 and then through thecheck valves 148, 149 in the pistons 100 and 102, respectively. At theend of the upward stroke there is high pressure air on both sides ofeach of the two pistons 100 and 102. Although one check valve has beenshown in each piston 100, 102, we preferably use several in each pistonto permit a freer flow of air from the space between the pistons duringclosing. The position of the parts at the end of the closing operationis depicted in FIG. 3.

It will be apparent that when the control piston 102 moves upwardly andreturns to its position of FIG. 3, it is once again pneumaticallycoupled to the pilot piston 100. Accordingly, when a subsequent openingoperation, the control piston 102 is moved downwardly, the pilot piston100 will move behind it in coupled follow-up relationship.

T he motor for controlling opening of the pilot valve For eflecting theabove-described downward movement of control piston 102 in order toinitiate a circuit breaker opening operation, a fluid motor 190 isprovided at the end of force-transmitting linkage 170. This fluid motor190 comprises a reciprocable piston 191 that is slidably mounted in astationary cylinder 192. When pressurized air is supplied to thecylinder space beneath piston 191, piston 191 moves rapidly upward,pivoting the crank 174 clockwise about its stationary pivot 174a andthereby rapidly pulling the operating rod 104 downwardly by forcetransmitted through the linkage 170. This downward movement of operatingrod 104 causes the pilot valve 70 to open, thereby initiating a circuitbreaker-opening operation, as described hereinabove.

When the piston 191 reaches the top of its upward pilot valve-openingstroke, as shown in FIG. 6, the pressurized fluid beneath it is ventedto a low pressure region, and the piston 191 quickly returns to itslowermost position of FIG. 5 in response to such venting. A suitablereset spring 193 is provided to facilitate this resetting operation. Theflow of pressurized fluid into and out of the cylinder spaced beneathpiston 191 is controlled by suitable threeway valve 195 that in itsnormal position vents the cylinder space to a low pressure region. Whenthe valve 195 is opened, as by energizing its solenoid operator 1%, thevalve establishes communication between a high pressure source and thecylinder space and also isolates the cylinder space from the lowpressure region. At the end of the upward opening stroke of piston 191,valve 195 is returned (by conventional means, not shown) to its normalposition to vent the cylinder space and permit resetting of piston 191.

It should be apparent that the fluid motor 190 needs to develop only arelatively low force in order to initiate an opening operation. This isthe case because this fluid motor does not directly actuate the blastvalve member 36 or the contacts 24 but merely operates the small pilotvalve 70. This pilot valve, in turn, initiates operation of therelatively massive blast valve and contacts by controlling the flow ofpressurized fluid into the actuating chamber 66 above the blastvalve-actuating piston 65.

Rapid build-up of force for opening circuit breaker When a circuitbreaker opening operation is to be initiated, the pressure in blastvalve-actuating chamber 66 can be built up very quickly because there isonly a very small volume upstream from the pilot valve 70 that needs tobe filled with pressurized fluid in order to develop a pressure build-upin the actuating chamber 66. In this respect, the actuating chamber 66itself is quite small, and the passageways '72, '73 and 69 between thepilot valve 70 and the actuating chamber 66 are quite short, as will beapparent from FIG. 3. Hence a very rapid pressure build-up in chamber 66is possible when the pilot valve 70 is opened. An important factor inkeeping the passages 72, 73, 69 short so as to permit a high rate ofpressure build-up is that the pilot valve 70 is located immediatelyadjacent the actuating chamber 66 and in a generally central positionwith respect to the actuating chamber 66.

It will be apparent that locating the pilot valve '70 generallycentrally of the actuating chamber 66 also contributes to thecompactness of the operating mechanism since no space outside the piston65 is required for the pilot valve. Locating the pneumatic coupling 100,132 in a cylinder space surrounded by annular actuating piston 65 alsocontributes to the compactness of the operating mechanism by obviatingthe need for external space to contain such coupling.

Rapid response to a closing signal It will be noted that theabove-described closing of the contacts was initated and controlledwithout requiring any simultaneous venting of a pressurized space aheadof the contact controlling mechanism. In certain prior mechanisms ofthis general type, it has been the practice to use pressurized fluid inthe blast valve closing space, such as 109, to hold the contacts open.When it was decided to close the contacts, this space was vented toatmosphere. When this venting reduced the pressure to a predeterminedlevel, closing was initiated and the closing speed was thereaftercontrolled by the rate of venting.

In certain circuit breaker applications, it is disadvantageous to relyupon such venting because it tends to be a rather slow operation thatunduly delays initiation of contact closing motion and unduly retardsthe closing motion once initiated. Also, closing characteristics tend tovary rather widely with variations in the initial fluid pressure holdingthe contacts open. This lack of precision in initiating and controllingthe closing operation can be a serious disadvantage in those circuitbreaker applications where it is desired to close the contact at aprecise instant after the occurrence of some predetermined event, suchas the insertion of a voltage-controlling resistor in the power circuit.

In the circuit breaker of the present invention, closing motion of thecontacts is initiated by releasing the latch 130. There is noappreciable opposition from pressurized fluid in the blast valve-closingchamber 1% at the time of such latch-release inasmuch as this chamber109 had previously been vented to atmosphere at the time the blast valvemember 36 closed, as described hereinabove. Hence, unlike in priormechanisms, there is no delay in the initiation of closing motion whilesuch space is be ing vented to develop a force for closing. In ourmechanism, closing force is available even before latch release inasmuchas there is a net force acting in a closing direction on the contacts assoon as this space 189 is vented, and such venting occurs long beforerelease of the latch 13%. This closing force which is available at thetime of latch-release can drive the contacts in a closing direction withno appreciable delay, and the speed of closing can be more preciselycontrolled since it does not depend upon the previously-used venting.Still further, using a fluid pressure-derived force for closing thecontacts has certain advantages over using'a spring-derived force inthat there is no force gradient to diminish the available force as thecontacts near their closed position. Thus, a

high closing force is available at the end of a closing operation toovercome the opposition of any magnetic forces that are developed atthis point by high currents flowing through the contacts when theyreestablish the power circuit at the end of a closing stroke.

Insensitivity of opening time to initial spacing between pilot andcontrol pistons It should be noted that the blast valve-opening timesand the contact-opening times are substantially independent of smallvariations in the length of the gap initially present between thepistons and N2 when a circuit breaker-opening operation is begun. Onefactor responsible for this substantial insensitivity to gap length isthat high pressure builds up so quickly above the booster piston 75 oncethe pilot valve member 71 starts moving toward open position that thepilot piston 100 is immedi ately driven into engagement with theadjacent downwardly-moving control piston 102. Thereafter, the openingspeed of the pilot piston 100 is the same as the opening speed of thecontrol piston 102. If a longer initial gap was present between thepistons 100 and 102, motion of the pilot piston would be initiated at aslightly later instant relative to the instant at which motion ofcontrol piston 102 had been initiated, but this late start would becompensated for by the higher initial speed at which the booster piston'75 would drive the pilot piston 100 when there was more space betweenpistons tilt) and 102. After a very short period, the pilot piston 160would have reached the same point in its opening travel as it would havereached had it started its opening travel slightly earlier. A slightlyearlier start at a lower speed would not appreciably increase the timefor pressure to build up to an effective level in blast valve actuatingchamber 66 because when the pilot valve is just beginning to open, verylittle air can flow past it, particularly if the opening speed isrelatively low. Thus, pressure builds up to an effective level in theactuating chamber 66 in about the same time irrespective of minorvariations in the length of the gap between pistons 1% and 102.Accordingly, if for any reason there should be minor variations in theinitial position of the control piston 102, these variations will notappreciably affect the circuit breaker opening times. a

While we have shown and described particular embodiments of ourinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from ourinvention in its broader aspects; and We therefore intend in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of theUnited States is:

1. In a gas blast circuit breaker comprising a contact movable from aclosed position to an open position to develop an arc and a blast valvemember movable from a closed position to an open position to create anarcextinguishing blast,

(a) a tank adapted to contain a supply of high pressure gas in whichsaid contact is located,

(b) a blast valve-actuating piston coupled to said movable blast valvemember,

(c) said piston having an opening surface on which pressurized fluid isadapted to act in a blast valveopening direction and a closing surfaceon which pressurized fluid is adapted to act in a blast valveclosingdirection,

(d) means for supplying high pressure fluid to the opening surface ofsaid piston to drive said piston through an opening stroke that openssaid blast valve member,

(e) actuating means coupled to said contact for transmittingcontact-opening motion from said blast valveactuating piston to saidcontact when said blast valve-actuating piston moves through saidopening stroke,

(f) means for supplying high pressure fluid to the closing surface ofsaid piston after said opening stroke to cause closing of said blastvalve member,

(g) means for venting the closing surface of said piston to a lowpressure region when said blast valve member is closed, thereby removingfrom said closing surface high pressure fluid that previously acted onsaid contact in an opening direction,

(h) closing means for causing the high pressure gas in said tank, whenthe closing surface of the blast valve piston is vented to a lowpressure region, to exert a net force on said contact acting in adirection to drive said contact toward closed position,

(i) latching means for holding said Contact in an open position againstsaid closing means when said closing surface of said piston is vented tosaid low pressure region,

(j) and closing control means for releasing said latching means topermit said closing means to drive said contact into closed position.

2. An electric circuit breaker of the gas-blast type comprising:

(a) a tank adapted to contain a supply of high pressure (b) a firstcontact within said tank,

. (c) a second contact Within said tank movable relative to said firstcontact between a closed position and a fully-open position,

(d) opening means for moving said second contact from said closed tosaid fully open position,

(e) means for rendering said opening means ineffective to exertcontinued opening force on said second contact when said second contacthas reached said fully open position,

(f) closing means for causing the high pressure gas in said tank, whensaid opening means is rendered ineffective, to exert a net force on saidsecond contact acting in a direction to drive said second contact towardclosed position,

(g) releasable latching means for holding said second contact in saidfully open position when said open- I ing means is rendered ineffective,

(h) and closing control means for releasing said latching means topermit said closing means to drive said second contact into closedposition.

3. The circuit breaker of claim 2 in combination with:

(a) a pilot valve having a normal condition from which it is operable toproduce operation of said opening means,

(b) pilot valve operating means releasably coupled to said pilot valvefor causing said pilot valve to operate and produce operation of saidopening means,

(c) means for releasing said pilot valve operating means from coupledrelation with said pilot valve to permit return of said pilot valve toits normal condition;

(d) means for returning said pilot valve operating means to coupledrelationship with said pilot valve,

(e) said closing control means being responsive to said return of thepilot valve operating means for effecting release of said latchingmeans.

4. An electric circuit breaker of the gas blast type comprising:

(a) a tank adapted to contain a supply of high pressure gas,

(b) a movable blast valve member movable from a normally-closed positionto an open position to create an arc-extinguishing blast of gas fromsaid tank,

(c) mounting structure located within said tank and having a passagewaytherein communicating with the high pressure air in said tank,

((1) a generally annular blast valve-controlling piston surrounding saidmounting structure and slidably mounted thereon,

(e) means coupling said annular piston to said movable blast valvemember,

(f) means defining a blast valve-opening chamber at one side of saidannular piston where pressurized fluid is adapted to exert a force fordriving said piston in a blast valve-opening direction,

(g) means defining a blast valve-closing chamber at the other side ofsaid annular piston where pressurized fluid is adapted to exert a forcefor driving said piston in a blast valve-closing direction,

(h) means including a normally-closed pilot valve located in saidmounting structure and openable to permit high pressure fluid to flowfrom said passageway in said mounting structure into said blastvalveopening chamber to drive said piston through a blast valve-openingstroke,

(i) and means controlled by said pilot valve for supplying high pressureair to said closing chamber to effect closing of said blast valve memberafter opening thereof.

5. The electric circuit breaker of claim 4 in combination with:

(a) a circuit-controlling contact movable between a closed position andan open position,

(b) contact-actuating means driven by said blast valve controllingpiston for imparting opening motion to said contact during a blastvalve-opening stroke,

(c) and means for holding said contact in open position when said blastvalve member closes.

6. The electric circuit breaker of claim 4 in combination with:

(a) a circuit-controlling contact movable between a closed position andan open position,

(b) contact-actuating means driven by said blast valve controllingpiston for imparting opening motion to said contact during a blastvalve-opening stroke,

(c) said contact actuating means comprising a forcetransmitting membercoupled to said contact and slidably mounted on said mounting structureand a plurality of rods coupled to said force-tranmitting member andprojecting therefrom through said blast valve closing chamber intoengagement with said blast valve-controlling piston,

(d) and means for holding said contact in open position when said blastvalve member closes.

7. The circuit breaker of claim 4 in which said mounting structure has acylinder space therein and said pilot valve comprises a movableflow-controlling pilot valve member, the circuit breaker furthercomprising:

(a) a pilot piston slidably mounted in said cylinder space and coupledto said movable pilot valve member,

(b) and means for controlling movement of said pilot piston comprising acontrol piston slidably mounted in said cylinder space adjacent saidpilot piston and pneumatically coupled to said pilot piston duringpredetermined movement of said control piston.

8. In a gas blast circuit breaker comprising a contact movable from aclosed position to an open position to develop an arc and a blast valvemember movable from a closed position to an open position to create anarcextinguishing blast,

(a) a blast valve actuating piston coupled to said movable blast valvemember,

(b) said actuating piston having an opening surface on which pressurizedfluid acts in a blast valveopening direction,

(c) a normally-closed pilot valve comprising a movable pilot valvemember having a normally-closed position for closing said pilot valveand an open position for opening said pilot valve,

(d) means including said normally-closed pilot valve for supplying highpressure fluid to said opening surface when said pilot valve is opened,thereby driving said actuating piston through a blast valve-openingstroke,

(e) a pilot piston coupled to said movable pilot valve member,

(f) a cylinder in which said pilot piston is slidably mounted,

(g) a control piston slidably mounted in said cylinder adjacent saidpilot piston,

(h) means for moving said control piston in a direction away from saidpilot piston,

(i) means for pneumatically coupling said pilot piston to said controlpiston so that said pilot piston moves in follow-up relation to saidcontrol piston and imparts opening movement to said movable pilot valvemember,

(j) means for rendering said pneumatic coupling inetfective after apredetermined movement of said control piston so that said movable pilotvalve member can return to its normally-closed position free of saidcontrol piston,

(k) means responsive to return of said pilot Valve member to its closedposition to effect closing of said blast valve member,

(l) actuating means coupled to said contact and driven by said blastvalve-actuating piston for imparting contact-opening movement to saidcontact in response to blast valve-opening movement of said blastvalveactuating piston,

(m) and latching means for holding said contact in an open positionfollowing closing of said blast valve member by its actuating piston.

9. The circuit breaker of claim 8 in which said blast valve-actuatingpiston has a closing surface on which pressurized fluid is adapted toact in a blast valve-closing direction and in which said means foreffecting closing of said blast valve member comprises means forsupplying high pressure fluid to said blast valve-closing surface whensaid movable pilot valve member returns to its closed position.

10. The circuit breaker of claim 8 in combination with:

(a) releasable restraining means for holding said con trol piston in aposition that it enters after causing .pilot valve-opening movement ofsaid pilot piston,

(b) closure-initiating means for returning said control piston to itsnormally-closed position adjacent said pilot piston in response torelease of said restraining means, i

(c) means responsive to passage of said control piston through anintermediate point in its return stroke for releasing said latchingmeans to permit said contact to close,

(d) and means responsive to release of said latching means to drive saidcontact into closed position.

11. In a gas blast circuit breaker comprising a contact movable from aclosed position to an open position to develop an arc and a blast valvemember movable from a closed position to an open position to create anarcextinguishing blast,

(a) a blast valve-actuating piston coupled to said movable blast valvemember,

(b) said actuating piston having an opening surface on which pressurizedfluid acts in a blast valve-opening direction,

(c) a normally-closed pilot valve comprising a movable pilot valvemember having a normally closed position for closing said pilot valveand an open position for opening said pilot valve,

(d) means including said normally-closed pilot valve for supplying highpressure gas to said opening surface when said pilot valve is opened,thereby driving said actuating piston through a blast valve-openingstroke,

(e) means for moving said movable pilot valve member into an openposition and for thereafter returning 16 said pilot valve member to itsnormally-closed position while said blast valve member is still open,

(f) means responsive to return of said pilot valve member to its closedposition to effect closing of said blast valve member,

(g) actuating means coupled to said contact and driven by said blastvalve-actuating piston for imparting contact-opening movement to saidcontact in response to blast valve-opening movement of said blastvalveactuating piston,

(h) and latching means for holding said contact in an open positionfollowing closing of said blast valve member by its actuating piston.

12. The circuit breaker of claim 11 in which said blast valve-actuatingpiston has a closing surface on which pressurized fluid is adapted toact in a blast valve-closing direction and in which said means foreffecting closing of said blast valve member comprises means forsupplying high pressure fluid to said blast valve-closing surface whensaid movable pilot valve member returns to its closed position.

13. The circuit breaker of claim 11 in which said means for moving saidpilot valve member into an open position comprises a driving memberreleasably coupled to said pilot valve member, and in which means isprovided for releasing the coupling between said driving member and saidpilot valve member after a predetermined movement of said driving memberto then permit closing movement of said pilot valve member.

14. The circuit breaker of claim 11 in which said means for moving saidpilot valve member into an open position comprises a driving memberreleasably coupled to said pilot valve member, and in which means isprovided for releasing the coupling between said driving member and saidpilot valve member after a predetermined movement of said driving memberto then permit closing movement of said pilot valve member, said circuitbreaker further comprising:

(a) releasable restraining means for holding said driving member in aposition that it enters after causing opening movement of said pilotvalve member,

(b) closure-initiating means for returning said driving member to aposition where it is coupled to said pilot valve member in response torelease of said restraining means,

(c) means responsive to passage of said driving member through anintermediate point in its return stroke for releasing said latchingmeans to permit said contact to close,

((1) and means responsive to release of said latching means to drivesaid contact into closed position.

15. In an electric circuit breaker comprising a contact movable from aclosed position to an open position to 7 effect circuit-interruption,

(a) a contact-actuating piston having an opening surface on whichpressurized fluid is adapted to act in a contact-opening direction,

(b) means for transmitting contact-opening motion from said piston tosaid contact when said piston moves in a contact-opening direction,

(c) means comprising a pilot valve for controlling the motion of saidcontact-actuating piston,

(d) said pilot valve comprising a movable pilot valve member having anormally-closed position for blocking pressurized fluid from reachingsaid opening surface and an open position for permitting .pressurizedfluid to reach said opening surface,

(e) a pilot piston coupled to said movable pilot valve member,

(f) a cylinder in which said pilot piston is slidably mounted,

(g) a'control piston slidably mounted in said cylinder adjacent saidpilot piston,

(h) means for moving said control piston in a direction away from saidpilot piston,

(i) means for pneumatically coupling said pilot piston to said controlpiston so that said pilot piston moves in follow-up relationship to saidcontrol piston and imparts opening movement to said pilot valve member,

(j) booster means effective when operative to apply a supplementalopening force to said pilot valve member to accelerate opening movementof said pilot valve member and to urge said pilot piston toward saidcontrol piston,

(k) and means controlled by initial opening movement of said pilot valvemember to render said booster means operative upon initial openingmovement of said .pilot valve member.

16. The circuit breaker of claim 15 in combination with anormally-closed blast valve member that is openable to produce a fluidblast that facilitates circuit interruption and means responsive tomovement of said contact-actuating piston in a contact-opening directionfor producing opening of said blast valve member.

18 17. The circuit breaker of claim 15 in combination with a housing athigh voltage surrounding said contact, said contact-actuating piston,said pilot valve, said pilot piston, said control piston, and saidbooster means; insulating means on which said housing is mounted; andmeans extending from said control piston to a location outside said tankfor imparting motion from said outside location to said control piston.

References Cited UNITED STATES PATENTS 2,783,337 2/1957 Beatty et al.200148 2,783,338 2/1957 Beatty 200-148 3,214,540 10/1965 Schrameck etal. 20 148 ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, Examin r.

1. IN A GAS BLAST CIRCUIT BREAKER COMPRISING A CONTACT MOVABLE FROM ACLOSED POSITION TO AN OPEN POSITION TO DEVELOP AN ARC AND A BLAST VALVEMEMBER MOVABLE FROM A CLOSED POSITION TO AN OPEN POSITION TO CREATE ANARCEXTINGUISHING BLAST, (A) A TANK ADAPTED TO CONTAIN A SUPPLY OF HIGHPRESSURE GAS IN WHICH SAID CONTACT IS LOCATED, (B) A BLASTVALVE-ACTUATING PISTON COUPLED TO SAID MOVABLE BLAST VALVE MEMBER, (C)SAID PISTON HAVING AN OPENING SURFACE ON WHICH PRESSURIZED FLUID ISADAPTED TO ACT IN A BLAST VALVEOPENING DIRECTION AND A CLOSING SURFACEON WHICH PRESSURIZED FLUID IS ADAPTED TO ACT IN A BLAST VALVECLOSINGDIRECTION, (D) MEANS FOR SUPPLYING HIGH PRESSURE FLUID TO THE OPENINGSURFACE OF SAID PISTON TO DRIVE SAID PISTON THROUGH AN OPENING STROKETHAT OPENS BLAST VALVE MEMBER, (E) ACTUATING MEANS COUPLED TO SAIDCONTACT FOR TRANSMITTING CONTACT-OPENING MOTION FROM SAID BLASTVALVEACTUATING PISTON TO SAID CONTACT WHEN SAID BLAST VALVE-ACTUATINGPISTON MOVES THROUGH SAID OPENING STROKES, (F) MEANS FOR SUPPLYING HIGHPRESSURE FLUID TO THE CLOSING SURFACE OF SAID PISTON AFTER SAID OPENINGSTROKE TO CAUSE CLOSING OF SAID BLAST VALVE MEMBER, (G) MEANS FORVENTING THE CLOSING SURFACE OF SAID PISTON TO A LOW PRESSURE REGION WHENSAID BLAST VALVE MEMBER IS CLOSED, THEREBY REMOVING FROM SAID CLOSINGSURFACE HIGH PRESSURE FLUID THAT PREVIOUSLY ACTED ON SAID CONTACT IN ANOPENING DIRECTION, (H) CLOSING MEANS FOR CAUSING THE HIGH PRESSURE GASIN SAID TANK, WHEN THE CLOSING SURFACE OF THE BLAST VALVE PISTON ISVENTED TO A LOW PRESSURE REGION, TO EXERT A NET FORCE ON SAID CONTACTACTING IN A DIRECTION TO DRIVE SAID CONTACT TOWARD CLOSED POSITION, (I)LATCHING MEANS FOR HOLDING SAID CONTACT IN AN OPEN POSITION AGAINST SAIDCLOSING MEANS WHEN SAID CLOSING SURFACE OF SAID PISTON IS VENTED TO SAIDLOW PRESSURE REGION, (J) AND CLOSING CONTROL MEANS FOR RELEASING SAIDLATCHING MEANS TO PERMIT SAID CLOSING MEANS TO DRIVE SAID CONTACT INTOCLOSED POSITION.